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Human aspects Landscape Ecosystem Population Individual Community Human aspects demands ecology to be a predictive science Conserve what? Biodiversity One species/population at a time What is a species or a population? Biological, Evolutionary, Ecological >15,000 species are listed as threatened with extinction worldwide by IUCN’s Red List International Union for Conservation of Nature and Natural Resources RedList conservation status Least concerned Near threatened Vulnerable Endangered Critically endangered Extinct Monitoring Restoration Conservation biology Ecology Social science Evolution Population viability analysis (PVA) Population viability PVA The probability of continued existence of a population, p(r>0) = ? The quantitative models to predict population extinction risks, p(r<0) = 1-p(r>0) PVA = Population model deterministic stochastic Stochasticity 1 Demographic stochasticity: Unpredictable changes in a population’s demography (how many individuals die, how many reproduce, etc.) caused by the randomness of individual fates. Stochasticity 1 Demographic stochasticity: Nt = Nt-1 x (e)r[1-(Nt-1/K) + ɛ(t)] r is not a constant but a result of chance event ri = f(b) - g(d), i = 1,2,3,…,Nt-1 Stochasticity 1 Demographic stochasticity: r = ? Individual 1 2 3 4 5 b d ri Stochasticity 2 Environmental stochasticity: Unpredictable changes in average demographic rates of a population, caused by vacillations in weather, food, predators, or other biotic and abiotic forces. Stochasticity 2 Environmental stochasticity: Nt = Nt-1 x (e)r[1-(Nt-1/K) + ɛ(t)] r is a constant at any given time but is adjusted by K and ɛ(t) rt = r[1-(Nt-1/K) + ɛ(t)] Stochasticity 3 Genetic stochasticity: Unpredictable changes in gene frequencies as a result of neutral processes such as genetic drift. Why would changes in gene frequencies affect population growth? Stochasticity 3 Genetic stochasticity: 1 0.75 0.5 0.25 A/B 0 A B birth b d r 50/50 1/1 0.2/0.8 0.5 0/100 1/1 0.2/0.8 0.2 Are these stochastic process? Higher temperature due to climate change increases disease risk and mortality? Higher temperature due to climate change select for genotypes with weak immunity? Higher temperature due to climate change changes life history to early reproduction? Stochasticity in PVA Stochasticity Population size Spatial scale Data requirement Environmental Any All Higher Demographic Small Local Lower Genetic Small Local Higher Major Categories of PVA Census- or count-based Stage-structured Spatial-structured Individually based Census- or count-based PVA Nt = λ x (Nt-1) λ = (Nt / Nt-1) ln(λ) = ln (Nt / Nt-1) mean[ln(λ)] = expected population growth Var[ln(λ)] = year-to-year variation in population growth Stage-structured PVA Population growth rate is a matrix of stagestructured fecundity and survival: f and p: fecundity and survival, both can be modeled using probability distribution PVA models Model Stochasticity Technique Census Var (population growth rate) Parametric Stage-structured Probability distribution of survival and fecundity Parametric Probability distribution of patch Spatial-structured colonization and extinction Parametric Chance event of survival, reproduction and movement of each individual Simulation Individually based Typical output of PVA Expected population growth rate Future population size Extinction risk Quasiextinction threshold Sensitivity Quasiextinction threshold (Nqe) The minimum number of individuals below which a population is likely to be critically and immediately imperiled. Example: Sensitivity in PVA Atlantic Loggerhead Sea Turtle Caretta caretta By ukanda Creative commons 2.0 Example: Sensitivity in PVA Two major threats to the loggerhead: loss and degradation of nesting habitat and direct harm to eggs and hatchlings drowning of individuals in the nets of fishing boats trawling for shrimp. Example: Sensitivity in PVA Crouse DL et al. 1987. A stage-based population model for loggerhead sea turtles and implications for conservation. Ecology 68: 1412–1423. Crowder LB et al. 1994. Predicting the impact of turtle excluder devices on loggerhead sea turtle populations. Ecological Applications, 4, 437-445. Example: Sensitivity in PVA Two major threats to the Loggerhead: loss and degradation of nesting habitat and direct harm to eggs and hatchlings drowning of individuals in the nets of fishing boats trawling for shrimp. Turtle Excluder Device (TED) NOAA Fisheries Example: Spatial-structured PVA Red-cockaded woodpecker (Picoides borealis) By Patrick Coin, Creative Common 2.5 Example: Spatial-structured PVA Major threat to red-cockaded woodpecker low breeding success limited by existing and slow generating natural tree holes Example: Spatial-structured PVA Letcher, BH et al. 1998. An individualbased, spatially-explicit simulation model of the population dynamics of the endangered red-cockaded woodpecker, Picoides borealis. Biological Conservation, 86, 1-14. The aggregation and number of territories (tree holes) to ensure population viability Population Viability Management (PVM) Island foxes (Urocyon littoralis) Population Viability Management (PVM) Major threat to the island foxes: Predation by golden eagle To conserve the fox, the best management is to remove eagles, which is extremely expensive Population Viability Management (PVM) Bakker, V. J., & Doak, D. F. 2008. Population viability management: ecological standards to guide adaptive management for rare species. Frontiers in Ecology and the Environment, 7, 158-165. Is there a viability analysis for community or ecosystem? Population viability analysis targets a clear parameter: extinction risk Community and ecosystem lack a definable modeling target